The function of a protein generally depends on adoption of a specific folding pattern, which in turn is determined by the side chain sequence along the polypeptide backbone. Here we show that the sequence-encoded structural information in peptides derived from yeast transcriptional activator GCN4 can be used to prepare hybrid alpha/beta-peptide foldamers that adopt helix bundle quaternary structures. Crystal structures of two hybrid alpha/beta-peptides are reported along with detailed structural comparison to alpha-peptides of analogous side chain sequence. There is considerable homology between alpha- and alpha/beta-peptides at the level of helical secondary structure, with modest but significant differences in the association geometry of helices in the quaternary structure.